testing: Add unreliable libc

testing/unreliable-libc/Makefile

@@ -0,0 +1,25 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -fPIC
+LDFLAGS = -shared
+TARGET = unreliable-libc.so
+SRCS = file.c
+OBJS = $(SRCS:.c=.o)
+
+.PHONY: all clean
+
+all: $(TARGET)
+
+$(TARGET): $(OBJS)
+	$(CC) $(LDFLAGS) -o $@ $^ -ldl
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+clean:
+	rm -f $(OBJS) $(TARGET)
+
+install: $(TARGET)
+	install -m 755 $(TARGET) /usr/local/lib
+
+uninstall:
+	rm -f /usr/local/lib/$(TARGET)

testing/unreliable-libc/file.c

@@ -0,0 +1,91 @@
+#define _GNU_SOURCE
+#include <sys/uio.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdio.h>
+#include <time.h>
+
+static double probabilities[] = {
+	[ENOSPC] = 0.01,
+	[EIO] = 0.01,
+};
+
+static bool chance(double probability)
+{
+	double event = drand48();
+	return event < probability;
+}
+
+static bool inject_fault(int error)
+{
+	double probability = probabilities[error];
+	if (chance(probability)) {
+		errno = error;
+		return true;
+	}
+	errno = 0;
+	return false;
+}
+
+static ssize_t (*libc_pwrite) (int, const void *, size_t, off_t);
+
+ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+	if (libc_pwrite == NULL) {
+		libc_pwrite = dlsym(RTLD_NEXT, "pwrite");
+	}
+	if (inject_fault(ENOSPC)) {
+		printf("%s: injecting fault NOSPC\n", __func__);
+		return -1;
+	}
+	if (inject_fault(EIO)) {
+		printf("%s: injecting fault EIO\n", __func__);
+		return -1;
+	}
+	return libc_pwrite(fd, buf, count, offset);
+}
+
+static ssize_t (*libc_pwritev) (int, const struct iovec *, int, off_t);
+
+ssize_t pwritev(int fd, const struct iovec *iov, int iovcnt, off_t offset)
+{
+	if (libc_pwritev == NULL) {
+		libc_pwritev = dlsym(RTLD_NEXT, "pwritev");
+	}
+	if (inject_fault(ENOSPC)) {
+		printf("%s: injecting fault NOSPC\n", __func__);
+		return -1;
+	}
+	if (inject_fault(EIO)) {
+		printf("%s: injecting fault EIO\n", __func__);
+		return -1;
+	}
+	return libc_pwritev(fd, iov, iovcnt, offset);
+}
+
+static int (*libc_fsync) (int);
+
+int fsync(int fd)
+{
+	if (libc_fsync == NULL) {
+		libc_fsync = dlsym(RTLD_NEXT, "fsync");
+	}
+	if (inject_fault(ENOSPC)) {
+		printf("%s: injecting fault NOSPC\n", __func__);
+		return -1;
+	}
+	if (inject_fault(EIO)) {
+		printf("%s: injecting fault EIO\n", __func__);
+		return -1;
+	}
+	return libc_fsync(fd);
+}
+
+__attribute__((constructor))
+static void init(void)
+{
+	srand48(time(NULL));
+}